Ambient temperature reference device

Abstract

A device for establishing an ambient temperature correction having (a) at least one reference surface which adequately represents the black body radiation spectrum of the air column between a long-path FTIR spectrometer and the infra-red source and (b) at least one means for shielding the reference surface from external sources of radiation gain or loss. In a preferred embodiment, the reference surface is made of thin metal having a blackened surface surrounded by an insulating shield. It is also preferred that a means for promoting positive air circulation across the reference surface or surfaces be included in the device of the present invention. This device is positioned in a location such that the field of view of the long-path FTIR spectrometer will be covered.

What is claim: 
     
       1. A device which is an ambient temperature reference for a long-path Fourier transform infrared spectrophotometer used to analyze a gas comprising: (a) a heat conductive surface which approximates the black body radiation spectrum of an air column between the spectrophotometer and an infrared source, and   (b) means for shielding the heat conductive surface from sources of radiation gain or loss.   
     
     
       2. The device of claim 1 in which a) is an aluminum sheet having a blackened surface. 
     
     
       3. The device of claim 1 in which the means for shielding the heat conductive surface b) is made of a heat reflective material. 
     
     
       4. The device of claim 1 in which an insulator is positioned between a) and b). 
     
     
       5. The device of claim 4 in which the insulator is selected from the group consisting of air, rigid or flexible foams, vacuum, cork, inorganic insulating materials, and wood or wood products. 
     
     
       6. The device of claim 1 in which the heat conductive surface is made of a material having a blackened surface selected from the group consisting of aluminum, copper, zinc, nickel, chromium, or heat conductive metal alloys. 
     
     
       7. The device of claim 1 in which the shielding means b) is made of a material selected from the group consisting of thermoplastic or thermoset resins, fiber-reinforced polymers, foamed plastics, pressed paper, bonded wood products, glass and metals. 
     
     
       8. The device of claim 1 in which a means for circulating ambient air so that it passes over the heat conductive surface a) is included. 
     
     
       9. The device of claim 8 in which the circulating means is an exhaust fan. 
     
     
       10. A method for correcting for ambient temperature the analytical results obtained by a long-path Fourier transform infrared spectrophotometer comprising placing the device of claim 1 in a location such that the heat conductive surface will be in the field of view of the spectrophotometer, collecting radiation from that heat conductive surface, and analyzing the infrared radiation collected from this surface with the spectrophotometer.